diff --git a/configure.ac b/configure.ac
index 6c36787f3..05523eef8 100644
--- a/configure.ac
+++ b/configure.ac
@@ -235,8 +235,8 @@ AC_SUBST(HAVE_SECCOMP, [$have_seccomp])
 # Look for aws-cpp-sdk-s3.
 AC_LANG_PUSH(C++)
 AC_CHECK_HEADERS([aws/s3/S3Client.h],
-  [AC_DEFINE([ENABLE_S3], [1], [Whether to enable S3 support via aws-sdk-cpp.])
-  enable_s3=1], [enable_s3=])
+  [AC_DEFINE([ENABLE_S3], [1], [Whether to enable S3 support via aws-sdk-cpp.]) enable_s3=1], 
+  [AC_DEFINE([ENABLE_S3], [0], [Whether to enable S3 support via aws-sdk-cpp.]) enable_s3=])
 AC_SUBST(ENABLE_S3, [$enable_s3])
 AC_LANG_POP(C++)
 
diff --git a/src/libstore/filetransfer.cc b/src/libstore/filetransfer.cc
index 514ab3bf9..2cf35ec83 100644
--- a/src/libstore/filetransfer.cc
+++ b/src/libstore/filetransfer.cc
@@ -7,7 +7,7 @@
 #include "finally.hh"
 #include "callback.hh"
 
-#ifdef ENABLE_S3
+#if ENABLE_S3
 #include <aws/core/client/ClientConfiguration.h>
 #endif
 
@@ -665,7 +665,7 @@ struct curlFileTransfer : public FileTransfer
         writeFull(wakeupPipe.writeSide.get(), " ");
     }
 
-#ifdef ENABLE_S3
+#if ENABLE_S3
     std::tuple<std::string, std::string, Store::Params> parseS3Uri(std::string uri)
     {
         auto [path, params] = splitUriAndParams(uri);
@@ -688,7 +688,7 @@ struct curlFileTransfer : public FileTransfer
         if (hasPrefix(request.uri, "s3://")) {
             // FIXME: do this on a worker thread
             try {
-#ifdef ENABLE_S3
+#if ENABLE_S3
                 auto [bucketName, key, params] = parseS3Uri(request.uri);
 
                 std::string profile = get(params, "profile").value_or("");